A "tepal" is a word for either a sepal or petal of an orchid flower, as sepals and petals often look similar. They appear in an outer whorl of three sepals and an inner whorl of three petals. The sepals, as the outer layer, enclose the flower buds, and open to reveal the petals and the column.

Orchid flowers are arranged with bilateral symmetry. One of the three sepals will be along the midline of the flower, and is called the dorsal sepal. The other two sepals are called lateral sepals (in lady slipper orchids the lateral sepals are fused together into a synsepal. All three sepals are fused in Masdeallia. A few other types of orchids have fused sepals, too.) The three petals also follow the bilateral symmetry. The one that's along the midline of the flower is opposite the dorsal sepal and called the labellum or "lip". The two lateral petals appear above the lateral sepals.

In most orchid flowers, the ovary (said to be "inferior" because it appears behind the flower) is twisted 180 degrees. There are a few orchids (such as certain Angraecums) in which this twist is absent, so that the flower is "upside down" with the labellum above the dorsal sepal.

Sepals and petals of orchid flowers come in all colors except blue and black. In some cases, they emit fragrances.

In some orchids, the labellum has a "spur", or nectary, which produces a sweet nectar for pollinators. Angraecum sesquipedale is perhaps the most famous of these, as it has a spur a foot and a half long (hence the Latin name "sesquipedale"). Charles Darwin predicted the existence of a moth with a proboscis long enough to reach down it; such a moth was later discovered.

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